Evaluating non-intrusive energy retrofits for the built heritage of historic centre of Oporto

S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 654–670 © 2017 WIT Press, www.witpress.com ISSN: 2058-8321 (paper format), ISSN: 2058-833X (online), http://www.witpress.com/journals DOI: 10.2495/HA-V1-N4-654-670 EVALUATING NON-INTRUSIVE ENERGY RETROFITS FOR THE BUILT HERITAGE OF THE HISTORIC CENTRE OF OPORTO S. ALVES & J.J. SENDRA Instituto Universitario de Arquitectura y Ciencias de la Construcción, Escuela Técnica Superior de Arquitectura, Universidad de Sevilla, Spain. ABSTRACT Traditional building materials and techniques should be preserved when selecting retrofit strategies. The most recurrent energy retrofit strategies proposed for the historic centre of Oporto are mainly focused on achieving, or even overlapping, the reference U-values established for the external envelope on national energy regulations, although historic sites are not obliged to comply with it. On the other hand, national cultural heritage preservation policies, by allowing alterations on these historic buildings interior, validate the adding of thermal insulation materials on internal walls. Nevertheless, these interventions may put to risk architectural patrimonial values, hence, sustainable ones. A more opportune intervention could be the enhancement of the windows performance, due to its most common bad state of conservation. This article analyses the performance of two non-intrusive retrofit strategies, in a representative model of these buildings: the enhancement of ventilation and the substitution of the single glazed windows for double glazed ones, and the two combined. On a first approach, using as a reference the heating loads limits established in the energy regulation of 2013 and the normative methodology, it is calculated the corresponding number of hours of daily heating use, in order to stand below these limits. The results obtained showed that this is attainable, in comfortable conditions of heating use. In order to achieve more accurate results and conclusions a dynamic simulation was performed using energy models, for the heating and cooling season. The enhancement of ventilation proved to be the most effective retrofit strategy. Keywords: energy efficiency, glazing, heritage buildings, historic centres, retrofitting, ventilation. 1 INTRODUCTION Vernacular architecture is an example of building within inherent sustainable characteristics: energy, materials and local resources. The Historic Centre of Oporto (HCO), inscribed as UNESCO’s World Heritage since 1996, is nowadays still threatened by the degradation of its urban built heritage, partly due to the exit of resident population. In order to invert the current tendency of desertification of the historic centre, it is crucial to adapt these buildings to a complexity of contemporary demands: thermal performance, technical systems, maintenance, ecological and recyclable materials, waste management and others. Nowadays, Europe’s approach to the heritage retrofitting of historic centres is associated with sustainability criteria, seeking to incorporate European regulations on building’s habitability and energy efficiency. Although the buildings located in historic areas are exempt from these regulations, studies were carried out [1, 2], recommending to the HCO buildings some energy retrofit strategies. In the opaque envelope (walls and roofs) it is proposed the adding of thermal insulation in order to approach the heat transfer coefficients (U-value) defined in the energy regulations, or even to overcome them. This approach tends to evaluate architecture only by its level of energy efficiency and external image. These recommendations can however enhance the loss of heritage values, such as original plaster work. The glazed areas are also the subject of proposals that can reduce both the U-value and the solar factor. These windows interventions are quite opportune, due to its most common state of conservation. S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 655 Besides some key factors acknowledged to determine the influence of daylighting in buildings thermal performance [3, 4] such as the fenestration factor (FF = window area/room area), the window wall ratio (WWR = glazing area/external facade area) and the effective aperture (EA = WWR × solar factor), it also recognized the importance of ventilation in the hygrothermal performance of buildings. Whereas, in Oporto, the cooling demand is about 10% of the heating demand, ventilation has a great impact in the winter season and ventilation may be responsible from 30% up to 50% of the total heating demand, which leads to a need to minimize the infiltration rates in order to reduce energy consumption [1]. This has been confirmed in different countries [5–8]. Recent studies [9] confirm that, in the HCO buildings, it is possible to obtain a significant reduction in the heating demand, improving the infiltration rate. Moreover, by measuring the airtightness in two non-refurbished characteristic buildings, some relations between the infiltration rates and the buildings’ morphological and typological characteristics were pointed out [10]. This article establishes an operative methodology aiming to position these buildings in relation to the Portuguese regulation on building’s energy demand, and the limits thereby defined, focusing on the heating loads as the most expressive comfort request in Oporto. According to this city’s climate, some authors [1] defend the notion of ‘real use’, which states that no cooling is used and the heating is used at 30% of its total load. On the other hand, we can determine the heating loads in a permanent regime and then define the hours of use in order to maintain the building below the energy loads limits. 2 ENERGY REGULATIONS Nowadays, Europe’s approach to the heritage retrofitting of historic centres is associated with sustainability criteria, seeking to incorporate European regulations on building’s habitability and energy efficiency. Regarding the thermal performance of buildings, the EPBD 2002/91/ CE [11] was incorporated in 2006 in the Portuguese regulation, comprising a revised version of the RCCTE [12], formerly published in 1990. The 2010 Energy Performance of Buildings Directive [13], and the 2012 Energy Efficiency Directive [14], generated in 2013 the current REH [15], regarding specifically the housing buildings. The REH establishes the parameters and methods of characterization of the energy performance of the housing buildings as well as promoting the improvement of its thermal performance. This regulation is mainly focused on new buildings, excluding ‘buildings integrated on classified sites, (…) whenever the accomplishment of the minimum energy performance requirements is susceptible to modify in an unacceptable way its character or feature’. Although the buildings located in historic areas are exempt from these regulations, studies were carried out [1, 2], recommending to the HCO buildings some energy retrofit strategies. In the opaque envelope (walls and roofs) it is often proposed the adding of thermal insulation in order to approach the heat transfer coefficients (U-value) defined in RCCTE, or even to overcome them. The glazed areas are also the subject of proposals that can reduce both the U-value and the solar factor. These windows interventions are quite opportune, due to its most common state of conservation and the energy potential of daylighting. 3 ARCHITECTURAL AND ENERGY HERITAGE Mostly erected between the 17th and the 19th centuries, the HCO buildings present morphologically a quite narrow width and a large length. The typology of the facades is mainly characterized by three windows per floor. These typologies create a harmonic street design, quite determinant in the UNESCO’s classification (Fig. 1). However, this historic centre should 656 S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) not be acknowledged merely as a set of harmonic facades to preserve. National cultural heritage preservation policies tend to interpret as the unique heritage value of these buildings, by allowing alterations on its building’s interior. We must explore the potential of non-intrusive retrofit strategies, once internal adding strategies may put to risk these building’s sustainable inherent value. In these buildings interior, there is both an architectural and energetic heritage to preserve, such as original plaster work and its internal wooden shutters (Figs 2 and 3). Figure 1: Street facades. Figure 2: Plaster work (left, middle) and wooden shutters (right). Figure 3: Wooden shutters detail (no scale). S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 657 These wooden shutters are an example of a refined architectural design. The masonry walls are dimensioned to embrace them, when they are in the opened position (yellow). Energetically speaking, as a shading device, they reduce the solar heating gains in summer and reduce the heating losses in winter. The window’s medium U-value is 5.1, when opened all day, achieving 3.4, when closed by night (Uref for glazing = 3.3). By proposing the adding of internal insulation on the walls, we may threaten the maintenance of these wooden shutters and the original design. If not, the risk of thermal bridges is also increased (blue). On the other hand, we may redesign the original carpentry and substitute the single glazing window for a double one. This is particularly opportune due to its most common bad state of conservation. In addition, this may lead us to an improvement of the air infiltration rate. In a previous study [16], two retrofit strategies were simulated in a representative model of these buildings, according to national RCCTE’s methodology: the enhancement of ventilation (R.1) and the substitution of single glazed windows for double glazed ones (R.2). Three models of typological retrofits were defined, using as a criterion the most usual ownership of these buildings. Analysis of data obtained evidenced the energetic potential of these buildings on its genesis. Considering the existing building, before any constructive retrofit intervention, it is possible to achieve a variable daily heating use, according to each dwelling pattern. The fact of closing the internal wooden shutters by night corresponds to a minimum hour gained in the heating use for all dwellings. Even with the shutters left open, the hours of heating use go from a minimum of 12 h to a maximum of 15 h and 17 h. The intervention R.1, using double glazing, allows one more hour gained of heating use. On the other hand, the enhancement of ventilation (R.2) corresponds to a gain of 2 h. The conjunction of these two strategies (R.3) permits a heating use from a minimum of 15 h to a maximum of 22 h. These results are rather superior to the previously referred notion of a real use of 30% of the heating loads, equivalent to 8 daily hours. In addition, it was possible to infer that the FF (FF = window area/room area) and the WWR (WWR = glazing area/external facade area) are morphological parameters determinant in the hygrothermal performance of the buildings. 4 METHODOLOGY In the study area, a representative model of these buildings was elected, taking into account both its length/width proportion and its facade characteristics (Fig. 4): three windows per floor comprising the existing three windows typologies. The main street facade is in São João street, 12 m width, west oriented (+22°), and the other one is in Mercadores street, 4 m width, east oriented (+13°). 4.1 Dwelling units definition This building has six storeys, lagged on the ground floor and top floor, due to the different street levels. The ground floor is usually for commerce, with a private staircase. The garret is non-habitable. This article defines three dwelling units (Fig. 5), corresponding to three models of typological retrofits, using as a criterion the most usual ownership of these buildings: A – one residence with five storeys; B – one residence per storey (four dwellings adapting top floor, B.4); C – one residence per storey and orientation (9 dwellings). 658 S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) Figure 4: West facade (left) and east facade (right). Dwelling unit CDwelling unit BDwelling unit A C.2.2 1.2.C C.3.2 B.1C.1.1 B.2 AC.1.2 C.4.1 B.3C.3.1 Staircase C.4.2 esacriatSesacriatS B.4 C.5.2 Figure 5: Dwelling units’ schemes. S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 659 Table 1: Morphological characterization of the dwelling units. Dwelling units Area Volume External surfaces Internal surfaces m2m3m2m2 Floor Window Wall Total btr = 0.3 btr = 0.6 btr = 0.6 btr = 0.9 A 490.8 1572.6 67.4 107.6 175.0 – 113.6 535.9 110.1 B.1 113.6 369.3 15.1 20.5 36.0 46.0 113.6 124.7 – B.2 109.4 372.0 15.1 27.8 42.9 50.7 – 127.9 – B.3 109.4 366.5 17.8 24.5 42.2 50.0 – 126.0 – B.4 109.4 342.4 13.8 25.6 39.4 46.7 – 117.8 109.4 C.1.1 57.4 186.5 10.4 10.2 20.6 20.5 57.4 58.7 – C.2.1 57.4 195.1 7.7 13.9 21.6 21.5 – 61.4 – C.3.1 57.4 192.2 10.4 10.8 21.3 21.2 – 60.5 – C.4.1 57.4 179.6 7.7 12.1 19.9 19.8 – 56.5 57.4 C.1.2 53.8 174.8 5.0 10.3 15.3 20.4 53.8 55.9 – C.2.2 49.0 166.5 7.3 14.0 21.3 21.4 – 53.6 – C.3.2 49.0 164.0 7.3 13.6 21.0 21.1 – 52.8 – C.4.2 49.0 153.2 6.1 13.5 19.6 19.7 – 49.4 – C.5.2 49.0 122.4 5.4 9.1 14.5 15.7 – 39.4 49.0 Table 2: Constructive characterization and heat transmittance of the building’s elements.  External finish Structure Internal finish U–value (W/m2K) Facade wall – W Lime mortar Granite 86 cm Plaster 1.87 Facade wall – E Lime mortar Granite 53 cm Plaster 2.39 Roof Ceramic tile Wood Plaster 2.30 Party wall – Granite 60 cm Plaster 2.01 Floor – Wood Plaster 1.20 Internal wall – Wood Plaster 1.20 Table 1 specifies the areas and volume of each dwelling unit, while Table 2 presents its constructive materials and corresponding heat transmittance (U-value). The building has a 5 mm single glazing, within a wooden frame, with internal wooden shutters (U-value = 5.1 W/m2K). 4.2 Simulation schedule Two different scenarios were established for the existing building (E). The simulation E.a corresponds to closing the shutters at night, presenting a medium U-value of 5.10 W/m2K. Simulation E.b supposes leaving the shutters open, presenting a medium U-value of 3.40 W/m2K. For the heating demand calculation, REH defines the use of a transparent inner curtain, equivalent to a solar factor (g-value) of 0.70 for single colourless glass and 0.63 660 S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) Table 3: Simulation schedule. ID Parameter Variable E.a Single glazing with internal curtain g-value = 0.70 Wooden shutters closed by night U = 3.40 W/m2K E.b Single glazing with internal curtain g-value = 0.70 Wooden shutters opened by night U = 5.10 W/m2K R.1 Double glazing with internal curtain g-value = 0.63 Wooden shutters closed by night U = 2.00 W/m2K R.2 Enhancement ventilation 0.60 ACH E.a R.3 R.1 R.2 for double colourless glass. For the existing building simulations, it was considered a natural ventilation with a value of 0.90 ACH, as established by the normative for non-classi- fied windows. Three retrofit strategies (R) were defined. The intervention R.1 corresponds to the replacement of single glazing for a double glazed one, which can be done by constructing a new wooden frame following the original design. The intervention R.2 establishes for natural ventilation the regulation’s minimum value of 0.60 ACH. The simulation R.3 comprises R.1 and R.2 altogether. Table 3 presents the different parameters defined and the respective variables affected. 4.3 Heating loads calculation All the calculation methodology is fully detailed in the normative [14]. The main changes in the new regulation (REH) comprise an actualization on the 2006’s climate data; the degree days (DD) for the heating season, on a basis of 18°C (formerly 20°C); corrections of several parameters due to altitude (M – heating season period, DD – number of degree days, θext – mean exterior temperature for both heating and cooling). The criteria for defining the heating demand limits (Ni) is now based on a reference building model, instead of the RCCTE’s parameters, which was determined by the buildings form factor and the degree days (DD) of the local climate. 4.3.1 Climatic parameters The values of the climatic parameters X associated to a specific zone are obtained from the reference values XREF for each established region, adjusted to zone altitude, z. The corrections due to altitude are linear, with a slope a, proportional to the difference between the zone altitude and a reference altitude for the region zREF, according to eqn (1): The climatic parameters applicable to the heating season are the following: DD – number of degree days, on an 18°C basis, corresponding to the conventional heating season; XX az z–  monthsorC 1 REFREF () ()() =+ ° S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 661 Table 4: Climatic parameters of the historic centre.  z M DD θext, i GSouth REF REF aREF aREF akWh/m2 m months month/km °C °C/km °C °C/km per month Oporto 94 6.2 2 1250 1600 9.9 –7 130 Historic centre 50 6.1 1180 10.2 130 M – duration of the heating season (months); θext, i – mean exterior temperature of the coldest month of the heating season; GSouth – monthly mean solar energy during the season, acquired on a vertical surface south oriented (kWh/m2 month). Table 4 shows the reference values for Oporto and those calculated for the historic centre, considering mean altitude of 50 m. Therefore, three winter climatic zones are established, according to the number of degree days (DD), on an 18°C basis: ‘I1’ – DD ≤ 1300; ‘I2’ – 1300 < DD ≤ 1800; ‘I3’ – DD > 1800. The historic centre is classified as an ‘I1’ winter climatic zone, corresponding to 6.1 months of heating season and 1180 degree days (DD) on an 18°C basis. The monthly medium value of the medium solar energy incident on a vertical surface south oriented, during the heating season (GSul), is 130 kWh/(m2 month). 4.3.2 Heating demand limits – Ni The maximum value for the heating energy demand (Ni) should be established considering reference values and conditions, according to eqn (2), being Qt – heat losses through the reference envelope in the heating season (kWh); Qv – heat losses due to reference ventilation in the heating season (kWh); Qg – net heat gains in the heating season (kWh); Ap – internal floor area (m2). NQ QQ A–/ (kWh/myear)] 2 itri refvei refgui refp,() ,() ,() 2 () () =+ For the winter climatic zone of Oporto, established in the REH as ‘I1’, the Uref values to be applied after 2015 are the ones showed in Table 5. Table 5: Uref values for the HCO. Envelope element Uref (W/m2 K) External or internal with a heat loss reduction coefficient btr > 0.7 Vertical opaque 0.40 Horizontal opaque 0.35 Adjacent to other buildings Vertical opaque 0.80 With a heat loss reduction coefficient btr ≤ 0.7 Horizontal opaque 0.70 Glazing (Uw) 2.80 In contact with terrain 0.50 662 S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) The reference value for heat losses due to ventilation through the envelope, Qve,i (ref), should be established considering a reference air infiltration rate, Rph (ref), equal to the building in study, with a maximum of 0.6 ACH. 4.4 Energy simulation models In order to achieve more accurate results and conclusions a dynamic simulation was performed, regarding the three retrofit strategies, as well as the original building, with the wooden shutters open by night (E.b). One of the most acknowledged assessment tools to test the hygrothermal performance of buildings and its energy demands is to create energy simulation models. In this investigation it was elected the Design Builder program that uses the Energy Plus dynamic simulation engine to generate performance data. Energy Plus is the US DOE building energy simulation program for modelling building heating, cooling, lighting, ventilating and other energy flows. Design Builder works with the main features and capabilities of BLAST and DOE-2. Once the program already includes the ASHRAE design weather data of Oporto, we introduced both the constructive and morphological data of the selected model for the heating and cooling load calculation. The operative temperature conditions (heating 18°C; cooling 25°C) for a residential use were settled based on a typical working week (week 18–23 h, weekend 8–23 h). In the remaining hours the system is considered to be turned off. This analysis was focused on the building as a whole (A) and on the intermediate dwelling units that have no heat losses to the ground floor or roof (B.2, B.3, C.2.1, C.2.2, C.3.1, C.3.2, C.4.2). The simulations comprised E.b – considered as the original, with wooden shutters opened all day and 0.90 ACH; R.1 – renovation with double glazing and 0.90 ACH; R.2 – enhancement of ventilation for 0.60 ACH; R.3 – combination of R.1 and R.2. The glazing characteristics are presented in Table 6. Table 6: Glazing characteristics. Calculated values E.b – single glazing 5 mm R.1, R.3 – double glazing 6 + 6 + 6 mm Total solar transmission 0.809 0.237 Direct solar transmission 0.775 0.136 Light transmission 0.881 0.173 U-value (ISO 10292/ EN673) (W/m2 K) 5.500 2.863 U-value (W/m2 K) 5.048 2.863 5 RESULTS AND DISCUSSION 5.1 Heating loads calculation Table 7 presents the heating loads (Nic) obtained for each dwelling unit and respective simulation for both the existent and retrofitted building and the limits defined by the regulation (Ni). These values were converted in daily hours of heating use, calculated in order to not exceed the calculated limits (Table 8). S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) 669 glazing for a double glazing registered from 11 to 17 h, while the conjunction of the two retrofit strategies achieved a maximum of 13–21 h. On the other hand, a dynamic simulation with energy models exposed the importance of the loss of solar gains in the heating season, when retrofitting single glazed windows by double glazed ones. However, the acoustic advantages of this strategy should be taken into account. It is important to associate this intervention with the enhancement of ventilation, in order to achieve an optimized solution. Energetically, the enhancement of ventilation as a single intervention proved to be the most unvarying in the heating energy savings with a minimum saving of 14% and a maximum of 26.4%. A primary measure to ensure the energy performance of these buildings is to take advantage of its architectural heritage, namely its typical internal wooden shutters, closing them by night in order to reduce the heat losses. Following the principle of non-intrusive interventions versus increase of the energy efficiency, we should improve the windows infiltration rate, which proved to be an important retrofit strategy. The most common bad state of conservation of the windows potentiates this intervention, by avoiding any cracks in the window assembly. In addition, it is particularly opportune for the replacement of single glazing for a double glazed one, by constructing a new wooden frame following the original design. These non-intrusive interventions, while not adding any new materials to the external envelope, enhance the architectural heritage values of these buildings. Hence, it is crucial to have an overall knowledge of these historic buildings’ morphological characteristics, once the FF and the WWR proved to be quite determinant in the heating energy savings, within the defined retrofit strategies. These results were obtained for a typological representative building of the HCO, although in a specific urban context, namely the streets width and respective east–west orientation. Further investigations should be developed embracing a wider range of situations. ACKNOWLEDGEMENTS This investigation was funded by FCT, Fundação para a Ciência e Tecnologia, with the grant reference SFRH/BD/103209/2014. REFERENCES [1] SRU (eds). Reabilitação de Edifícios do Centro Histórico do Porto: Guia de Termos de Referência para o Desempenho Energético-Ambiental, SRU: Porto, 2010. [2] OERN (eds). Manual de Apoio ao Projecto de Reabilitação de Edifícios Antigo, OERN: Porto, 2012. [3] Saridar, S. & Elkadi, H., The impact of applying recent façade technology on daylighting performance in buildings in eastern Mediterranean. Building and Environment, 37, pp. 1205–1212, 2002. DOI: 10.1016/S0360-1323(01)00095-6 [4] Freire, R.Z., Mazuroski, W., Abadie, M.O. & Mendes, N., Capacitive effect on the heat transfer through building glazing systems. Applied Energy, 88, pp. 4310–4319, 2011. DOI: 10.1016/j.apenergy.2011.04.006 [5] Papadopoulos, A.M., Teodosiou, T.G. & Karatzas, K.D., Feasibility of energy saving measures in urban buildings – The impact of energy prices and the acceptable pay back criterion. Energy and Buildings, 34, pp. 455–466, 2002. DOI: 10.1016/S0378- 7788(01)00129-3 [6] Tommerup, H. & Svendsen, S., Energy savings in Danish residential building stock. Energy and Buildings, 38, pp. 618–626, 2006. DOI: 10.1016/j.enbuild.2005.08.017 670 S. Alves & J.J. Sendra, Int. J. of Herit. Archit., Vol. 1, No. 4 (2017) [7] Domínguez, S., Sendra, J.J., León, A.L. & Esquivas, P.M., Towards an energy demand reduction in social housing buildings: Envelope system optimization strategies. Energies, 5, pp. 2263–2287, 2012. DOI: 10.3390/en5072263 [8] Binamu A., Integrating Building Design Properties “Air Tightness” and Ventilation Heat Recovery for Minimum Heating Energy Consumption in Cold Climates. Dissertation. Tampere University of Technology, 2002. [9] Alves, S. & Sendra, J.J., Rehabilitation and energy efficiency – Methodological strategies for the Historic Centre of Oporto. Book of Proceedings: Heritage 2012 – Heritage and Sustainable Development. Chapter 3 – Heritage and Environment. pp. 395. Green Lines Institute, eBook ISBN: 978-989-95671-8-4, 2012. [10] Alves, S., Fernández-Agüera, J. & Sendra, J.J., Infiltration rate performance of buildings in the historic centre of Oporto. Informes de la Construcción 66(535), 2014. [11] EPDB 2002/91/EC, Directive of the European Parliament and of the Council on the Energy Performance of Buildings, 16 December 2002. http://eur-lex.europa.eu/legalcontent/EN/TXT/?uri=CELEX%3A32002L0091, accessed 29.11.2016. [12] RCCTE (2006) Regulamento das Características de Comportamento Térmico de Edifícios, Decreto-Lei n.º 80/ 2006 de 4 de Abril, 2006. http://www.adene.pt/sites/default/ files/24682513.pdf, accessed 29.11.2016. [13] EPDB 2010/31/EU, Directive of the European Parliament and of the Council on the Energy Performance of Buildings, 19 May 2010. http://eur-lex.europa.eu/legal-content/ en/TXT/?uri=celex%3A32010L0031, accessed 29.11.2016. [14] EED 2012/27/EU, Directive of the European Parliament and of the Council on Energy Efficiency, 25 October 2012. http://eur-lex.europa.eu/legal-content/en/TXT/?uri= celex%3A32012L0027, accessed 29.11.2016. [15] REH, Regulamento de Desempenho Energético dos Edifícios de Habitação, Decreto- Lei 118/2013 de 20 Agosto, 2013. https://www.academiaadene.pt/download/pt/ decretolei-1182013-anotado-v0_2013-11-13.pdf, accessed 29.11.2016. [16] Alves S. & Sendra J.J, Evaluating constructive and typological retrofits in solid masonry historic buildings. WIT Transactions on the Built Environment, 153, WIT Press, 2015, pp. 381–391. DOI: 10.2495/STR150321.